You probably know that you can connect an external monitor to the video connector on your laptop and switch the display from the laptop’s small LCD to the larger external monitor. In this situation, you see the same image on both the laptop’s LCD and the external monitor.
But if you’re running Windows XP Professional or Windows XP Home on your laptop and have a supported video adapter and a recent video adapter driver installed, when you connect an external monitor to your laptop, you can configure a multiple monitor environment using the DualView feature. You can then extend your desktop across two monitors, so that you can surf the Internet on one monitor while you take notes in Word on the other monitor. Here's how.
The importance of the video adapter and driver
It’s safe to assume that all laptops sold with Windows XP preinstalled on them will, by virtue of the Designed For Microsoft Windows XP sticker, support Windows XP’s DualView feature. However, many pre-XP laptops can also access Windows XP’s DualView feature if they have a video adapter and a video adapter driver that support DualView.
Laptops have long supported an external monitor connection, but they have traditionally been able to display only the same image on both the laptop’s LCD and the external monitor. For the laptop to be able to display different images on different monitors, the graphics controller on the video adapter must provide DualView functionality. In other words, the video adapter must support the simultaneous operation of two monitors with different screen frequencies. Furthermore, this support must share the available memory on the video adapter between the monitors that are connected to the internal and external ports. For example, if the video adapter has 16 MB of available memory, the memory on the video adapter is divided such that each monitor has access to 8 MB.
Now, just because the video adapter provides DualView functionality, that doesn’t mean that it is automatically available. That’s only the first level of support. The second level of support is, of course, provided by the video adapter driver, which must be able to register two distinct instances of the same display adapter—one for the first video output port and one for the second output port—with the operating system.
Then, on the third level, there has to be some type of software that allows the operating system to access the feature. Prior to Windows XP, you would have had to use some sort of utility provided by the video adapter’s manufacturer or another third-party program. However, now that Windows XP provides native support for the third level, all you need to have is support for the first two levels.
Right out of the box, Windows XP provides video adapter drivers that support DualView for only three popular laptop-based video adapters with built-in DualView functionality:
If your laptop has a different video adapter, you’ll need to turn elsewhere. To begin with, you should check out Windows Update to see if an officially supported Windows XP driver update is available for your video adapter.
Your next stop should be your laptop manufacturer’s support site, the reason being that most laptop manufacturers customize the video adapters/drivers specifically for their systems. So a generically available driver for your laptop’s video adapter might not work reliably, if at all.
However, if the previous stop leads to a dead end, you can try the video adapter manufacturer’s site. It may indeed have a driver that will work. If you're using ATI RAGE Mobility drivers, see the tip box below for more information on configuring them for use with DualView.
ATI RAGE Mobility drivers and DualView
One of my laptops is a Dell Inspiron 3800 with an ATI RAGE Mobility M1 video adapter in it. When I first installed Windows XP, the default adapter driver didn’t provide support for DualView. At a later date, I downloaded an updated adapter driver from the Windows Update site and suddenly had support for DualView. At the time, I didn’t really go beyond experimenting with DualView once or twice to see if it did indeed work. And it did, beautifully.
Some time later, I decided to wipe my hard disk and reinstall Windows XP. I then visited the Windows Update site to reinstall all the updates, including a new ATI RAGE Mobility M1 video adapter driver. However, much to my chagrin, DualView was nowhere to be found.
I searched the Dell site for an updated adapter driver and found one. After extracting the release notes, I discovered a line that simply read: No Extended Desktop Or DualView Support.
There was no explanation at all about why an updated driver didn’t support a built-in feature that was supported in a previous driver. I then looked high and low for an older version of the adapter driver, but hit a dead end.
Being a newsgroup aficionado, I turned there for information and learned that I wasn’t the only person who was missing DualView support in an ATI RAGE Mobility adapter driver. In fact, the reports mentioned the same problem with a variety of ATI RAGE Mobility products installed in laptops from various manufacturers. And yet there were other reports from folks with the exact same ATI RAGE Mobility adapter installed in other laptops that had no problem at all—DualView was working perfectly. I then stumbled upon a report that stated that certain laptop manufacturers had decided to intentionally disable DualView support in the ATI RAGE Mobility adapter driver due to unspecified problems. Reading further, I learned that there was a way to reenable DualView support by making a slight change in the registry.
In the case of my Dell Inspiron 3800 with an ATI RAGE Mobility M1 video adapter running with driver version 18.104.22.16879, the registry edit worked. DualView appears to be working perfectly. If you have a laptop with an ATI RAGE Mobility M1 video adapter and don’t have access to DualView, you may want to experiment with this simple registry edit.
To begin, you should make sure that you have the most recent adapter driver for the ATI RAGE Mobility M1 video adapter that you can find. Most important, launch System Restore and create a restore point. That way, you have an additional fallback option. The first one is the Roll Back Driver button on the Driver tab of the video adapter Properties sheet, which you can access via Device Manager.
To change the registry, launch the Registry Editor by accessing the Run dialog box and typing Regedit.exe in the Open text box. Once the Registry Editor is up and running, pull down the Edit menu and select the Find command. When you see the Find dialog box, type DisableDualView in the Find What text box and click Find Next.
When you locate the first instance of the DisableDualView setting, which will be a DWORD data type, double-click it. When you see the Edit DWORD Value dialog box, change the Value data setting from 1 to 0 and click OK. Then, press F3 to repeat the search and change each instance of the DisableDualView setting that you encounter. (On my system, I discovered nine such instances of the DisableDualView setting.) Once you complete the operation, reboot your system. You should then be able to access and take advantage of the DualView feature.
Activating the DualView feature
If you have a video adapter with built-in DualView functionality and a video adapter driver that can access the feature, activating Windows XP’s DualView feature is a snap. To begin, you should shut down your laptop and make sure the external monitor is turned off. Then connect the monitor to the video connector on your laptop.
Once you have Windows XP up and running again, turn on the external monitor. If your laptop is like most, you’ll have a special hotkey keystroke combination that will allow you to switch between the individual monitors as well as activate both monitors at the same time. You should switch the setting such that only the laptop monitor is activated. Doing so will ensure that the second monitor is properly configured.
Then, access the Display Properties dialog box by right-clicking the desktop and selecting the Properties command. Next, select the Settings tab. When you do, your dialog box should look similar to the one shown in Figure A.
|If DualView is accessible, you’ll see a graphic showing two monitor icons in the center of the Settings tab.|
To continue, select the second monitor icon in the graphic. When you see that the Extend My Windows Desktop Onto This Monitor check box is enabled, select it, as shown in Figure B. At this point, if you hover your mouse over the monitor graphics, you’ll see that number 1 is listed as the Primary Display and number 2 is listed as the Secondary Display with a set of numbers in parentheses.
|When you select the check box, the second monitor icon in the graphic is enabled.|
For example, with a screen resolution of 800 by 600, the coordinates would be (800,0). This set of coordinates indicates at what location the second monitor icon starts. If you wish, you can click and drag either monitor icon to any position. When you’re finished, click Apply. As soon as you do, your second monitor will come to life.
Depending on how you positioned the monitor icons, you may want to make sure that they correctly represent your actual monitor’s physical positions. To investigate, click the Identify button at the bottom of the dialog box. You’ll then see a large number appear on each monitor icon showing which monitor corresponds with each icon.
To complete the DualView configuration, just click OK to close the Display Properties dialog box. You can then begin using the two monitors to spread out your work.
DualView isn't just for laptops
DualView can be used on desktop computers too. When you use Windows XP’s Multiple Monitor feature, you’re actually using more than one video adapter in your system—one for each monitor. However, there are high-end video adapters out there that actually have multiple video ports on the same unit. When you use these types of video adapters in a desktop system, they will actually use DualView.
You can find these types of video adapters, usually referred to as Dual-Head video adapters, from such manufacturers as ATI Technologies, Appian Graphics, and Matrox.
If you want to learn more about Windows XP’s DualView feature, you can investigate the following articles on the Microsoft Knowledge Base:
Greg Shultz is a freelance Technical Writer. Previously, he has worked as Documentation Specialist in the software industry, a Technical Support Specialist in educational industry, and a Technical Journalist in the computer publishing industry.